This invention relates to communication technologies generally and particularly to midplane systems.
Freed from government restrictions in the telecommunication industry, traditional operators, such as the telephone companies, face intensive competition from a new breed of network operators, such as the wireless and the Internet service providers. In order to remain competitive, the traditional operators need platforms that allow them to quickly roll out services in response to changes in market conditions. On the other hand, because the new network operators often lack the resources of a traditional operator, they need equipment that is flexible, cost effective, readily maintainable and yet still compatible with the same packaging as traditional telecommunication systems.
Although desktop-class systems may have sufficient processing capabilities to drive applications such as Internet access, they lack the level of fault tolerance that is suitable for the mentioned telecommunication operators. Specifically, replacing a failed communications card in a desktop system takes significant amount of time. It involves turning off the system and removing the appropriate packaging. Additionally, this replacement process may also involve removing attached cables, fitting the replacement and reassembling the system.
One alternative solution is a prior art midplane system as shown in FIG. 1. In particular, chassis 100 contains midplane 102. Midplane 102 is a circuit board that provides sockets for plug-in cards such as main card 104 and transition card 106 to plug into. Unlike the desktop-class system, a midplane system thus allows for easy loading and removal of communication cards without having to tamper with the cabling and the assembly of the system.
Moreover, in a typical midplane system, main card 104 contains the processing engine and has a higher failure rate than passive components. Conversely, transition card 106 mostly provides Input/Output (hereinafter I/O) termination and has a lower failure rate. This deliberate separation of functionality is an attempt to maintain a high level of fault tolerance for the midplane system. More specifically, replacing transition card 106 likely involves reconfiguring I/O and rearranging physical cabling, which are both time-consuming and susceptible to errors. Therefore, implementing transition card 106 with a low failure rate is likely to result in infrequent changes of the card and a reduced probability of encountering undesirable delays and errors that are associated with the card changes. On the other hand, unlike transition card 106, swapping out main card 104 does not involve the mentioned reconfiguration and rearrangement. Thus, placing core processing on an easily exchangeable communication card, such as main card 104, helps to avoid disrupting operations of the midplane system.
However, a midplane system that communicates with optical networks has optical interfaces on main card 104. As a result, replacing main,card 104 would also involve rearranging physical cabling. As has been discussed above, this rearrangement leads to unwanted delay and errors. Hence, an improved method and apparatus is needed to address the fault tolerance issues of a midplane system discussed above.